Researchers spent three years looking at the eating habits of children in the city and discovered that some were skipping meals and others scoffed junk food after school.
Children were told to keep five-day diaries of what they ate at home and school. They were even given scales to measure exact amounts.
Typical home meals included fish fingers, spaghetti hoops, tinned ravioli and frozen chips.
But these less-than-healthy dishes paled in comparison with one child's lunch box. Hull University researchers were aghast when they found a 10-year-old boy carrying 11 full-size chocolate bars.
At first they thought the lad, who was not overweight, was selling on the treats to other pupils. But further investigation revealed that the 1,440 calories contained in the bars was his regular daily lunch.
Lisa Gatenby, a nutritionist, said: "I was shocked when I saw what was in his lunch box.
"He later told me he ate a cooked breakfast and had a takeaway burger for his tea."
Despite the shocking discovery, researchers found that fewer children were snacking on their way to school.